The present invention relates to ionization illumination systems and particularly to a high pressure sodium (HPS) illumination system.
It is well known to have lamp or luminaire systems in which the luminaire element contains a gas which may be ionized by electric excitation and when the luminaire is electrically excited, the ionized gas provides illumination. One of the disadvantages of ionization illumination, as opposed to incandescent lamp illumination or illumination from light emitting diodes (LED's), is that a relatively high voltage is required to initially excite the gaseous element into ionization so as to produce illumination. However a great advantage of ionization illumination over incandescent lamp illumination is that after the luminaire element is electrically excited into an illuminated state a relatively very small amount of continuing alternating power is required to produce a relatively large amount of light output.
High pressure sodium lamps are combined with starting circuitry, ballasting circuitry, sockets and reflectors into assemblies called luminaires, These luminaires or lighting systems are particularly designed to be excited into a state of ionized illumination by normal 110-120 volt alternating current which is a 60 Hertz or cycle current.
A start up circuit is normally part of the lighting system. The start up circuit, which is connected to the 110-120 AC supply, provides high voltage pulses to the lamp to excite the gas into an ionized state. After such state is attained the start up circuit becomes dorment in favor of application to the luminaire of a substantially low AC voltage required to maintain ionization of the gaseous element. It has been found that 60 Hertz power of relatively low current per unit illumination may be used to maintain ionization. The ballasting circuit controls the amount of power drawn by the high pressure sodium lamp after the arc has been established by the starting circuit.
This provides a large amount of lumens obtained from the amount of electricity used to keep the luminaire in a state of illumination, thus providing relatively energy efficient illumination.
Commercially produced high pressure sodium luminaires have been designed to operate from standard 115 volt 60 Hertz alternating current, which is normal utility power in the United States of America. However, the availability of utility power is usually limited in many applications requiring portable or emergency lighting. This limited distribution of utility power limits the use of high energy efficiency HPS luminaire systems unless an alternate source of power is provided.